A system described in U.S. Pat. No. 7,040,108 accomplished four modes of operation by integrating four heat exchanger circuits of which two only functioned as evaporators and two only functioned as condensers.
Dynamic transitions generally are a function of switching between two evaporators or switching between two condensers that may be available to a given compressor as accomplished by U.S. Pat. No. 7,040,108. While not common, this would historically be accomplished through use of 2-way, 3-way, or 4-way solenoid/pilot operated valves. When modes were switched, the solenoid would shut one refrigerant path and simultaneously open another. This created undesirable noise and vibrations. It could cause the compressor to experience a sudden spike in pressure which was often followed by a period of low system pressure causing the compressor to experience a brief period of run-away or over-speed.
What is therefore needed is a system that allows an HVAC system to gain the cost and operational efficiencies as well as the flexibility of directly performing four modes of operation. The four modes of operation including, heating, cooling, direct water heating, and cogeneration.
The invention preferably includes multi-split heat pump heat exchangers to eliminate the need for two indoor and two outdoor single mode heat exchangers, as in the prior art, and eliminate the fanless outdoor evaporator of the prior art to provide direct space heating rather than hydronic supported space heating.
Further the configuration of this invention allows quiet smooth transitions over a period of greater than 90 seconds without run-away.
Such a configuration may also overcome the limitations of the of the prior art including a pilot operated solenoid valve and its inability to reliably operate under the pressure conditions of a refrigerant system involving more than 2 heat exchanger circuits and to avoid the harsh transitions associated with the solenoid valves. Such a configuration may allow the system to provide a means to balance the charge between more than 2 differently sized heat exchangers within a single heat pump system and provide a dynamic transition between different modes of operation without executing an off-cycle.